title: Prevention of RhoA activation and cofilin-mediated actin polymerization mediates the antihypertrophic effect of adenosine receptor agonists in angiotensin II- and endothelin-1-treated cardiomyocytes.
abstract: Adenosine receptor activation has been shown to be associated with diminution of cardiac hypertrophy and it has been suggested that endogenously produced adenosine may serve to blunt pro-hypertrophic processes. In the present study, we determined the effects of two pro-hypertrophic stimuli, angiotensin II (Ang II, 100 nM) and endothelin-1 (ET-1, 10 nM) on Ras homolog gene family, member A (RhoA)/Rho-associated, coiled-coil containing protein kinase (ROCK) activation in cultured neonatal rat ventricular myocytes and whether the latter serves as a target for the anti-hypertrophic effect of adenosine receptor activation. Both hypertrophic stimuli potently increased RhoA activity with peak activation occurring 15-30 min following agonist addition. These effects were associated with significantly increased phosphorylation (inactivation) of cofilin, a downstream mediator of RhoA, an increase in actin polymerization, and increased activation and nuclear import of p38 mitogen activated protein kinase. The ability of both Ang II and ET-1 to activate the RhoA pathway was completely prevented by the adenosine A1 receptor agonist N (6)-cyclopentyladenosine, the A2a receptor agonist 2-p-(2-carboxyethyl)-phenethylamino-5'-N-ethylcarboxamidoadenosine, the A3 receptor agonist N (6)-(3-iodobenzyl)adenosine-5'-methyluronamide as well as the nonspecific adenosine analog 2-chloro adenosine. All effects of specific receptor agonists were prevented by their respective receptor antagonists. Moreover, all adenosine agonists prevented either Ang II- or ET-1-induced hypertrophy, a property shared by the RhoA inhibitor Clostridium botulinum C3 exoenzyme, the ROCK inhibitor Y-27632 or the actin depolymerizing agent latrunculin B. Our study therefore demonstrates that both Ang II and ET-1 can activate the RhoA pathway and that prevention of the hypertrophic response to both agonists by adenosine receptor activation is mediated by prevention of RhoA stimulation and actin polymerization.
authors.affiliation: Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, N6A 5C1, Canada.
authors.forename: Asad
authors.initials: A
authors.lastname: Zeidan
authors.forename: Xiaohong Tracey
authors.initials: XT
authors.lastname: Gan
authors.forename: Ashley
authors.initials: A
authors.lastname: Thomas
authors.forename: Morris
authors.initials: M
authors.lastname: Karmazyn
mesh_terms: D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D006332:Cardiomegaly / Q000201:enzymology / Q000473:pathology / Q000517:prevention & control*; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D019332:Endothelin-1 / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D008954:Models, Biological; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D058105:Polymerization / Q000187:drug effects*; D021381:Protein Transport / Q000187:drug effects; D058906:Purinergic P1 Receptor Agonists / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D019332:Endothelin-1; D058906:Purinergic P1 Receptor Agonists; D000804:Angiotensin II; D048051:p38 Mitogen-Activated Protein Kinases; D020742:rhoA GTP-Binding Protein